Date: Thu, 13 Feb 2014 13:15:01 -0500 From: Garrett Wollman <wollman@bimajority.org> To: John-Mark Gurney <jmg@funkthat.com> Cc: FreeBSD Net <freebsd-net@freebsd.org> Subject: Re: Use of contiguous physical memory in cxgbe driver Message-ID: <21245.2981.568824.19800@hergotha.csail.mit.edu> In-Reply-To: <20140213180736.GA34851@funkthat.com> References: <21216.22944.314697.179039@hergotha.csail.mit.edu> <201402111348.52135.jhb@freebsd.org> <CAJ-VmonCdNQPUCQwm0OhqQ3Kt_7x6-g-JwGVZQfzWTgrDYfmqw@mail.gmail.com> <201402121446.19278.jhb@freebsd.org> <21244.20212.423983.960018@hergotha.csail.mit.edu> <20140213075651.GY34851@funkthat.com> <21245.1163.754141.154430@hergotha.csail.mit.edu> <20140213180736.GA34851@funkthat.com>
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<<On Thu, 13 Feb 2014 10:07:36 -0800, John-Mark Gurney <jmg@funkthat.com> said: >> [I wrote:] >> It's very easy to get to that state if the driver insists on getting >> three physically contiguous pages (which is what it takes to allocate >> a single 9k cluster) > Well, if you're using a cheap NIC that can't do scatter/gather DMA, > then you get what you pay for... No, I'm using expensive 10G NICs, like the Chelsio ones mentioned in the subject header. They have no trouble doing s/g (subject to some reasonable limits on chain length). The problem is when the drivers insist on physical contiguity anyway. I finally gave up and hacked the cxgbe driver never to use anything longer than a physical page. -GAWollman
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